Most hydrocarbon emissions from vehicle engines are created during an engine start, particularly before the vehicle catalyst is warm. The use of alternative fuels, such as those including alcohol, can help to reduce hydrocarbon emissions. However, starting a vehicle with such fuels can be difficult due to the low volatility of the fuel, especially in cold weather. Thus, a number of methods may be used to achieve reliable start of the engine while reducing emissions. Some example methods include starting an engine with hydrogen gas, which is a gas in any terrestrial condition, and has high volatility while producing minimal start emissions.
One example of an engine using hydrogen gas during a direct start is described in Cerny et al. in WO 2007/101,329. Cerny et al. describe a system including an electrolysis system for producing hydrogen gas and oxygen gas from water. The hydrogen gas is directed along a line to a storage reservoir, from which hydrogen gas may be directed to the engine or intake manifold for subsequent combustion. The oxygen gas is directed along a separate line, to either be vented to the atmosphere or injected into vehicle engine cylinders.
The inventors herein have recognized potential issues with such an approach. As one example, separation of the hydrogen gas and oxygen gas, and direction of these gasses along separate lines, may require several extra components, thereby increasing the number of components and/or space required for the system. Further, following the above approach, any inaccuracies in the delivery of the hydrogen and/or oxygen may lead to inaccurate ratios of constituents in the combustion chamber, and thus may increase emissions.
Some of the above issues may be addressed by a method for starting a vehicle engine having a plurality of cylinders. The method may include generating hydrogen gas and oxygen gas onboard the vehicle from water, and maintaining the hydrogen gas and oxygen gas together as a gaseous mixture. The method may further include injecting the gaseous mixture to at least one cylinder of the engine during an engine start. In particular example, the oxygen gas and hydrogen gas are maintained together from the generation to delivery to a cylinder.
This method has the potential benefits of reducing hydrocarbon emissions while achieving reliable engine starting. By maintaining the hydrogen gas and oxygen gas together, a known stoichiometric ratio of the gasses (e.g., Brown's gas, oxyhydrogen) with good combustibility and low emissions is ready for injection to the engine during a start, such as a direct start. The gaseous mixture has minimal hydrocarbon emissions and thus particularly complements vehicle engines employing alcohol fuels, and/or other alternative fuels with low hydrocarbon emissions but low volatility. Further, by maintaining the hydrogen gas and oxygen gas together as a gaseous mixture ready for injection to the engine, the number of components needed for control and delivery of the gaseous mixture to the engine may be reduced.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.